How to convert a MultiDict to nested dictionary using Python

A MultiDict is a dictionary-like object that holds multiple values for the same key, making it a useful data structure for processing forms and query strings. It is a subclass of the Python built-in dictionary and behaves similarly. In some use cases, we may need to convert a MultiDict to a nested dictionary, where each key corresponds to a dictionary of values. In this article, we will discuss the steps required to convert a MultiDict to a nested dictionary in Python.

First of all, install multidict library by writing the following command in your command line or terminal:

pip install multidict

Steps to convert a MultiDict to a nested dictionary:

1. Import multidict library
2. Create a MultiDict using the MultiDict() constructor
3. Iterate over the items in the MultiDict
4. For each item, check if the key already exists in the nested dictionary.
5. If the key exists, append the value to the list of values associated with the key.
6. If the key does not exist, create a new entry in the nested dictionary with the key and a list of values containing the value from the MultiDict.

Example 1:

In the following example, we convert a MultiDict to a nested dictionary.

Python3

# import multidict
from multidict import MultiDict

# create a MultiDict
data = MultiDict([('key1', 'value1'), ('key2', 'value2'),
                  ('key1', 'value3')])

# initialize a nested dictionary
nested_dict = {}

# iterate over the items in the MultiDict
for key, value in data.items():
    # check if the key exists in the nested dictionary
    if key in nested_dict:
        # append the value to the list of values
        # associated with the key
        nested_dict[key].append(value)
    else:
        # create a new entry in the nested dictionary
        # with the key and a list of values
        nested_dict[key] = [value]

# output the nested dictionary
print(nested_dict)

Output:

In this example, Create a MultiDict with keys ‘key1’ and ‘key2’ and multiple values. Iterate over the items, add value to the existing key’s list or create a new entry with key and value in the nested dictionary. Output is a nested dictionary with keys and lists of values associated with each.

Example 2:

In the following example, we convert a MultiDict to a nested dictionary.

Python3

# import multidict
from multidict import MultiDict

# create a MultiDict
data = MultiDict([('fruit', 'apple'), ('color', 'red'),
                  ('fruit', 'banana'), ('color', 'yellow')])

# initialize a nested dictionary
nested_dict = {}

# iterate over the items in the MultiDict
for key, value in data.items():
    # check if the key exists in the nested dictionary
    if key in nested_dict:
        # append the value to the list of values
        # associated with the key
        nested_dict[key].append(value)
    else:
        # create a new entry in the nested dictionary
        # with the key and a list of values
        nested_dict[key] = [value]

# output the nested dictionary
print(nested_dict)

Output:

In this example, create a MultiDict with two keys ‘fruit’ and ‘color’ with multiple values. Iterate over the items, if the key exists, append its value to the list, else create a new entry in the nested dictionary with the key and list of values. The final output is a nested dictionary with keys and lists of values associated with each key.